1. Field of the Invention
This invention relates to the use of aluminum oxide (Al.sub.2 O.sub.3) as a coating for reactor internals. Specifically, it has been discovered that the internals of metallic reactors and other metallic chemical process components (i.e., piping, cyclones) which are exposed to catalyst utilized in various chemical processes, react with the catalyst to form compounds which eventually coat the catalyst causing a loss of catalytic activity or otherwise inhibiting catalyst performance. In particular this invention relates to coating with aluminum oxide reactor internals for processes for the oxidation of n-butane to maleic anhydride which utilize a catalyst comprising a compound of vanadium, phosphorus and oxygen.
2. Description of the Prior Art
Reactor vessels and associated hardware and piping used in refinery and chemical processes are typically constructed of carbon or low alloy steel. Where corrosion is a problem, stainless steel or other corrosion resistant materials including aluminum oxide are employed.
A focus of the instant invention are catalytic processes for the oxidation of hydrocarbons which utilize catalysts comprising a compound of vanadium, phosphorus and oxygen and which operate at elevated temperatures. Typically, the reactors for these processes have been fabricated from carbon or low alloy steel. It has been discovered that steel surfaces exposed to such catalyst at elevated temperatures react with the catalyst to produce contaminants which coat the exterior of the catalyst thereby inhibiting catalyst performance. This problem becomes particularly troublesome in fluid bed reactors where catalyst particles are continually circulating as the catalyst particles are suspended in a stream of upward flowing gases, and where contaminants are easily commingled with the catalyst and the circulating catalyst has numerous opportunities to contact metallic surfaces.
The above phenomena and the ill effects caused thereby have been detected in fluid bed processes for the catalytic oxidation of n-butane to maleic anhydride. In this process the catalyst comprising a compound of vanadium, phosphorus and oxygen and operating in carbon or low alloy steel (including stainless steel) reactors eventually acquire iron containing contaminants on the catalyst surface which causes a loss of catalyst activity as well as a loss in catalyst fluidization quality.
An object of this invention is a means to eliminate the production of such contaminants in processes for the catalytic oxidation of n-butane to maleic anhydride thereby maintaining the activity and performance of the catalyst used therein.